1. Field of the Invention
Embodiments of the present invention generally relate to methods and apparatus for semiconductor device fabrication, and more specifically, to methods and apparatus for detecting proper positioning of semiconductor substrates.
2. Description of the Related Art
Each manufacturing step performed on a semiconductor or flat panel display substrate incrementally increases its value to the associated manufacturer. At any given time, a manufacturer may have in its inventory hundreds, or even thousands of in-process substrates. During the device manufacturing process, a given substrate may be moved, placed, and retrieved dozens of times or more between and among different processing and storage locations within the fabrication facility. For the most part, such movement, placement, and retrieval of in-process substrates within the fabrication facility occurs automatically, and/or without direct operator intervention or supervision, thereby reducing the potential for damage to valuable in-process inventory due to operator error.
However, a risk of damage to in-process substrates still exists, despite the implementation of automated substrate handling technology. For example, even if a substrate has been successfully delivered to the general vicinity of a particular substrate support element (e.g., to a substrate support platform, a transfer surface, an end effector, a set of support pins, or the like), the substrate may fail to assume an expected position or spatial orientation relative to the support element (e.g., upon initial placement thereon), or fail to remain in such expected position or spatial orientation. Such improper positioning and/or spatial orientation, if not timely corrected or otherwise compensated for, can quickly lead to substrate damage, e.g., via a subsequent device formation step that proceeds improperly due to a gross error in substrate positioning or orientation, or via an unintended collision between the substrate and an automated end effector during a subsequent substrate transfer step. Moreover, damage to equipment or contamination of subsequent or proximate substrates may further occur.
Thus, there is a need for effective methods and apparatus for reducing the risk of substrate and/or equipment damage arising from improper substrate positioning and/or spatial orientation relative to associated support elements.